The semiconductor industry has grown according to Moore's Law for the last fifty years. Moore's Law roughly holds that the number of transistors on an integrated circuit doubles about every two years. Inherent in this formulation of is the limitation that the progression of transistor density is two-dimensional, and that at some point physics imposes a limit on how small devices can be.
Recently, manufacturers have developed processes that extend device structures into the third dimension to increase processing capability. Such devices generally feature large numbers of material layers deposited sequentially on a substrate. In some cases, over 100 layers may be formed. When so many layers are formed sequentially, non-uniformities in each layer can multiply, resulting in unusable structures. Current layer formation processes and apparatus typically produce non-uniformities that are not suitable for three-dimensional structures. Thus, new processes and apparatus are needed for forming extremely uniform layers on a substrate.